The invention relates to a gas meter calibration device for hydrogen-oxygen mixtures which comprises a connection for a gas meter.
In plants in which hydrogen or oxygen is produced, such as, for example, in water electrolysis plants, the oxygen gas resulting must constantly be monitored for contamination by hydrogen and the hydrogen gas resulting must constantly be monitored for contamination by oxygen so as to prevent the danger of explosion. It is known that the lower explosion limit for hydrogen-oxygen mixtures lies in the range of approximately 4% by volume of contaminant gas. This applies both to hydrogen contaminants in oxygen and oxygen contaminants in hydrogen. This monitoring process is carried out with the aid of gas meters.
The gas meters must operate accurately to prevent all danger of explosion. These meters must be accurately calibrated to achieve this.
In a known calibration method a gas meter is supplied with a gas mixture in which the hydrogen or the oxygen component is replaced by an inert gas, for example nitrogen. By replacing a component by inert gas, this calibration mixture itself is safeguarded against any danger of explosion.
Since, however, the inert gas has physical properties different to those of the replaced hydrogen or oxygen gas, the properties of the inert gas calibration mixture must be translated to a hydrogen-oxygen mixture. This method thereby becomes inaccurate, as the reverse calculation always entails uncertainties. It is therefore impossible to accurately calibrate a gas meter for hydrogen-oxygen mixtures using this method.
Another known calibration method employs hydrogen-oxygen calibration gases which are already fully premixed and are supplied in gas bottles. This is highly complex, as a large number of gas mixtures of differing compositions are required to accurately calibrate a gas meter. This method therefore gives rise to high expenditure. Moreover, for safety reasons the hydrogen-oxygen gas mixtures which are available have concentrations of the respective foreign gas of a maximum of approximately 1.5% by volume in order to definitely remain below the lower explosion limit. This means that gas meters can only be calibrated over a narrow range.